<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>

<body>
    <script>
        var r = /^([1-9][0-9]?|0)$/;
        console.log(r.test('100'));//false

        var r1 = /^([12][0-9][0-9]|[1-9][0-9]?|0)$/
        var str1 = '100';
        console.log(r1.test(str1)); // true

    </script>
</body>

</html>